1. Volume 20, Issue 4, Pages 619-626 (April 2013)
A LOV2 Domain-Based Optogenetic Tool to Control Protein Degradation and Cellular Function 
Christian Renicke, Daniel Schuster, Svetlana Usherenko, Lars-Oliver Essen, Christof Taxis 
Chemistry & Biology 
Volume 20, Issue 4, Pages (April 2013)
DOI: /j.chembiol
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2. Figure 1 Development of a psd
(A) Schematic design of the psd module in the dark and lit states. In darkness, the cODC1 degron is inactive and the fusion protein is stable. Upon irradiation by blue light, the degron is activated and induces proteasomal degradation of the fusion protein.
(B) Realization of the psd module. Different constructs were tested for the ability to work as a psd using the target protein RFP. Construct a was derived by inserting seven amino acids from the cODC degron (MSCAQES, ODC7) between P616 and D617 of AtLOV2; construct b was derived by fusing 23 amino acids from cODC1 (MSCAQESITSLYKKAGSENLYFQ, ODC23) after P616 (psd module; the full sequence of the construct can be found in Figure S1); construct c was derived by fusing the same sequence after E614, closer to the Jα helix; and construct d was derived by using the full cODC1 degron (positive control, ODC36). The relative position of the cysteine-alanine (CA) motif to the Jα domain can be approximated from the drawing. AtLOV2 alone fused to RFP (construct e) was used as negative control. RFP fluorescence was observed by microscopy in dark and lit conditions.
See also Figure S1.
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3. Figure 2 Light Control of Protein Stability with the psd Module
(A) Blue light activates the psd module. Fluorescence microscopy images of yeast cells expressing PADH1-RFP-AtLOV2 or PADH1-RFP-psd (plasmid based) pregrown in the dark were incubated in the absence or presence of blue light (LED lamp, 470 nm, 10 μmol m−2 s−1) for 4 hr. Scale bar, 4 μm.
(B) Reversibility of psd-module-induced target protein depletion. Yeast cells expressing PADH1-RFP or PADH1-RFP-psd (plasmid based) were grown in liquid medium in the dark. After removal of the first sample (t = 0 hr), cells were exposed to blue light (LED lamp, 465 nm, 30 μmol m−2 s−1). After 4 hr of light exposure, cells were transferred to the dark. Samples taken at the indicated time points were subjected to alkaline lysis and immunoblotting. Antibodies against tRFP and Tub1 (loading control) were used for detection (negative control; neg c). Please note that even though the RFP-AtLOV2 fusion protein is seven amino acids shorter than RFP-psd, it runs slightly slower in SDS-PAGE.
(C) Kinetics of psd-module-induced target protein depletion after exposure to blue light. Yeast cells expressing PADH1-RFP or PADH1-RFP-psd (plasmid based) were grown in liquid medium in the dark. After removal of the first sample (t = 0 hr), cells were exposed to blue light (LED lamp, 465 nm, 30 μmol m−2 s−1). Curves are the means of RFP and RFP-psd protein amounts obtained from six immunoblots (representative result shown in Figure S2C). Error bars indicate SEM.
(D) Measurement of psd-module-induced target protein destabilization. Yeast cells expressing PADH1-RFP-psd (plasmid based) were grown in liquid medium in the dark. After removal of the first sample (t = 0 hr), cycloheximide (chx) was added to stop protein synthesis; cells were kept in the dark or exposed to blue light (LED lamp, 465 nm, 30 μmol m−2 s−1) for the rest of the experiment. Curves are the means of RFP-psd protein amounts obtained from nine independent measurements. Error bars indicate SEM. The representative result is shown in Figure S2D.
See also Figure S2.
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4. Figure 3
Characterization of psd Module Behavior on a Macroscopic Level
(A) Input-output characteristics of the psd module in a plate assay. A neutral density gradient (uppermost image on the left) was used to generate a blue light gradient (465 nm; intensity from 0.04 to 3.54 μmol m−2 s−1), which was applied on cells expressing PTDH3-RFP-psd (plasmid based). Yeast cell growth is shown in the middle image on the left (bar size, 1 cm), RFP fluorescence intensity is represented as a heat map (lower left image). Background corrected fluorescence (right graph, red curve) was plotted together with calculated blue light intensity (blue curve).
(B) Yeast photography. The RFP-psd module was inserted chromosomally at the 3′ end of ADE2 (YDS91). Cells were grown for 3 days at 25°C on solid medium and irradiated by blue light (465 nm, 10 μmol m−2 s−1) using a mask with an inverted black-and-white image of the “Alte Universität” in Marburg, Germany (right image). The resulting yeast photograph is shown on the left side. Bar size, 1 cm.
See also Figure S3.
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5. Figure 4 Control of Cell Cycle Events by Light
(A) Serial dilutions (1:5; first spot about 2,400 cells) of control (YDS28), clb2Δdb-3myc-psd, and ΔNsic1-3myc-psd (plasmid-encoded) cells were spotted on YPD plates and incubated 3 days at 25°C in absence or presence of blue light (465 nm, 20 μmol m−2 s−1).
(B) The same yeast strains as in (A) were pregrown under blue light and then exposed to blue light (465 nm, 30 μmol m−2 s−1) for 5 hr or kept in darkness over the same time and finally used for image acquisition. Differential interference contrast and fluorescence images (RFP-Tub1) were used to categorize cell cycle stages according to the examples shown in the lower left. Scale bar, 3 μm. Circular graphs (outer ring: 5 hr darkness; inner ring: growth exposed to blue light) show the mean distribution of cell cycle stages obtained from four biological replicates counting at least 100 cells for each replicate.
See also Figure S4.
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6. Figure 5 Generation of Conditional Mutants Using the psd Module
(A) The gene encoding for the psd module together with RFP or 3myc was fused chromosomally to the 3′ end of CDC5 (YCT1316), CDC14 (YCT1315), MCM1 (YDS120), PMA1 (YCT1338), CDC48 (YDS175), UFD1 (YDS187), NPL4 (YDS191), SEC62 (YDS174), and SEC63 (YDS188). Serial dilutions of cells (1:5 dilutions; first spot about 2400 cells) were spotted on YPD plates and incubated three days at 25°C in absence or presence of blue light (465 nm, 20 μmol m−2 s−1).
(B) Blue-light induced cell patterning. sec62-RFP-psd mutant cells (YDS82) were spread on solid medium and blue light (465 nm, 7 μmol m−2 s−1) was applied for 3 days. The star-shaped mask (shown in the left image) was used to block light in the center of the plate. Growth of the yeast cells is shown on the right side. Bar size, 1 cm.
See also Figure S5.
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7. Figure 6 In Silico Modeling of psd Module Behavior
(A) Graphical representation of the TinkerCell model for light-induced degradation of the psd module. A detailed description of the model and the values used for our simulations can be found in the Experimental Procedures section. For generation of the graphs, total amounts of PSD (PSDdark + PSDlit) were calculated.
(B) Simulated amounts of PSDtotal synthesized with different promoter strength (PP1 = 1; 2; 4; 8) at increasing light intensities corresponding to light fluxes from 0 to 30 μmol m−2 s−1.
(C) Light response of the psd module. Normalized PSDtotal amounts at different light intensities [0.04 to 3.54 μmol m−2 s−1 plotted as k(hν) values] simulated with TinkerCell compared to mean values of normalized fluorescence in cells exposed to a blue-light gradient (n = 3). Error bars, SD. The representative experiment is shown in Figure 3A and Figure S3C).
See also Figure S6 and Table S3.
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8. Chemistry & Biology 2013 20, 619-626DOI: (10. 1016/j. chembiol. 2013
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